1. Field of the Invention
This invention is a method of fracturing rocks using high pressure fluid.
2. Description of the Prior Art
The prior art discloses many methods to fracture rocks using hydraulic fluids. In the U.S. Pat. No. 3,507,540 (D. Silverman), there is disclosed a method of cutting large diameter bore holes in rocks. To accomplish its objective: a circular channel is first cut, and rock is broken off this channel by a transverse fracture by inserting an inflated packer near the bottom of the channel and then pass fracturing liquid through the packer. In an alternate embodiment, small diameter holes are drilled in the column of rock to the depth of the channel. Then a packer is placed in a central hole and inflated with fracturing liquid being injected beneath the packer into the volume at the base of the hole. Whichever of the two Silverman methods are employed, a fracture propagates from one drilled hole to another to detach a relatively large core. Neither of these are used with my method wherein a three-dimensional fracture propagates from a slot in the bottom of a single small drilled hole to the free surface. Thus, I employ a simpler procedure with less cutting in a near surface fracturing method.
The United States Patent to C. E. Reistle, Jr., (2,547,778) shows a borehole with a fracture directed in a radial outward direction (see FIG. 2 therein). And the U.S. Pat. No. 3,018,095 (J. F. Radlinger) discloses a method using hydraulic fracturing between underground wells. Both of these two inventions differ from my invention in that they are not for removing rocks from a free surface. In still another patent (U.S. Pat. No. 3,988,037 to J. P. Denisart et al.), a hole has hydraulic fluid compacted into it with a piston therein to cause tensile stress cracks. Shock waves generated by the piston do the fracturing. My invention does not depend on piston strokes to fracture rocks but does depend on the materials' properties of low tensile strength and the geometry of the slot. A lower fluid pressure using less energy to induce a rock fracture is possible because of the slot geometry and the fracture it initiates parallel to the free surface. My invention has as its object the breaking of a hard material whose tensile strength is much less than its compressive strength which would include rocks such as granite, limestone, sandstone, marble, etc. It does not depend on creating an impact velocity sufficient to cause cracks in the material, i.e. dynamic loading, such as with a water hammer. The two U.S. Pat. Nos. (4,123,108 and 4,141,592) to Erik V. Lavon disclose such dynamic loading systems.